Gold Districts of California
Location. The Hammonton district is in south-central Yuba County along the lower
Yuba River about 10 miles east of Marysville. It is a major dredge field that extends
along the river about eight miles. It also is known as the Yuba River district.
History. The river and streams here were first worked 'during the gold rush by
small-scale placer methods. However, this soon ceased because the river level was raised
by a large influx of hydraulic mine tailings. Bucket-line dredging began in the district
in 1903 under the direction of W. P. Hammon. In 1905 his interests were taken over bv Yuba
Consolidated Gold Fields, which had just been organized. This concern perfected
large-scale bucket-line dredging here into one of the most efficient methods for mining
placer gold. Yuba Dredge No. 20 was one of the largest gold dredges in existence. The
district was dredged almost continuously from 1903 to 1968 and was the principal source of
gold in California for some time. The estimated total output from dredging was estimated
in 1964 at 4.8 million ounces.
However, operations have been gradually curtailed; in 1967 only two dredges were
operating. On October 1, 1968 the last dredge was shut down, thus ending a major industry
that had existed for nearly 70 years. More than a billion cubic yards of gold-bearing
gravels were dredged. The extensive piles of gravel have become increasingly important as
sources of aggregate.
Gold-Bearing Gravels. The gold-bearing gravels are in and south of the Yuba
River, which flows west-southwest through the area. Digging depths range from 60 to 80
feet on the upper end to 100 to 125 feet in the vicinity of the town of Hammonton. As much
as 45 feet of the upper gravels are hydraulic mine tailings. Bedrock in the upper eastern
end of the field consists of metamorphic rocks, while, in the central and western
portions, the gravels are underlain by clay. The gold recoveries have been as follows: 12
cents/yd in 1915-16; 14-15 cents/yd in 1920-22; 8-9 cents/yd in 1928-29; 12 cents/yd in
1948-49, and 16.56 cents/yd in 1959. The hydraulic tailings were reported to have averaged
6 cents/yd at the old price. The gravels are medium to fine and are free-washing. Minor
amounts of platinum were recovered. According to the April, 1960 issue of Mining World, in
1959 Yuba Cons. reported four dredges treated 16,642,265 cu. yds. with an average content
of 16.56 cents per yard. Reserves in the area were estimated to be about 93 million cu.
yds. Estimates are that about 235 million yds. of gold-bearing gravels are in the field
but beyond depths of existing equipment.
Operations. Hammon and Davis, 1903-05 (bought by Yuba Cons.), two dredges;
Marysville Dredging Co., 1906-25 (bought by Yuba Cons.), five dredges; Pacific Gold
Dredging Co., 1916-23, one dredge; Yuba Cons. Goldfields, 1905-1968, 21 dredges, not all
worked at the same time.
Excerpt from: Gold Districts of California, by: W.B. Clark, California
Department of Conservation, Division of Mines and Geology, Bulletin 193, 1970.
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